It is often required that the symbols associated with the keys of a keyboard be changed. This is particularly true where the keyboard is used as an input terminal to provide data and/or function control inputs to a data processor. An example of this would be a computer terminal used in the education field to train students in different foreign languages.
Recently there have been innovations in output display technology. The printing mechanism on typewriters allows changes from one character font or language to another by changing the print "ball" or "wheel". On printers or video displays using dot matrix character generation, new characters can be defined by altering what is stored in the section of memory referred to as character generator memory. This section of memory can and historically has been permanent. Recently there have been devices that allow the character generator memory to be altered or modified, either by action at the device or by a series of commands transmitted through a communication interface from a remote location. There is a need to alter the character representations on the keyboard keys to correspond with the changes in the display characters.
Prior methods for changing the symbols or character representations of each key of a keyboard required that each keycap be changed. This entailed considerable time, for example, ten to fifteen minutes for the typical keyboard. In addition special tools in the hands of a reasonably skilled mechanic are also required.
The present invention contemplates a device wherein the symbols or character representations associated with the keys of a keyboard may be changed in a very short time, e.g., seconds and which permits the change to be done by anyone.
More specifically the present invention contemplates an overlay having openings for each of the keys of the keyboard. The overlay is mounted on the keyboard. Each of the openings has a sloped portion above its adjacent key which provides a highly visible surface bearing the symbols or character representations associated with each key. The overlay is exchangeable with other overlays bearing different symbols as required by each program.